The present application relates generally to the field of vehicle seat belt systems which provide occupant protection during a dynamic vehicle impact event. More specifically, the disclosure relates to an improved tongue mechanism for a seat belt system.
Motor vehicles have been equipped with seat belt systems coupled or integrated with seat systems. During a vehicle dynamic impact event, the seat belt system restrains an occupant with a seat belt or webbing to the seat system, providing protection to the occupant. Among the conventional seat belt systems, a three point seat belt system is generally known and employed. The typical method of configuring a three point seat belt system is to connect the seat belt or webbing fixedly at one end to the vehicle or seat system, connect the other end fixedly to the seat belt retractor, and slideably couple a tongue to the webbing between its ends. The tongue then may be detachably coupled to a buckle mechanism positioned on the side of the seat opposite to the anchor and retractor connections of the webbing. Thereby, when the tongue is latched to the buckle mechanism, the webbing forms a lap portion which extends across the lap of the occupant between the anchor and tongue connections of the webbing; and forms a shoulder portion which extends diagonally across the torso of the occupant and over the shoulder of the occupant, between the tongue and retractor connections of the webbing.
It has been known to make a tongue mechanism slideable along the length of a continuous loop of webbing to allow the occupant to adjust the lengths of the lap and shoulder portions of the seat belt. It has also been known to construct a tongue mechanism that includes a cinch mechanism, having a lock bar that is driven by belt tension from the latching of the tongue and buckle mechanisms to cinch the webbing of the seat belt system. There are two primary types of tongue mechanisms having cinch mechanisms. The first type are non-free falling tongues, which the cinch mechanism engages the webbing as soon as the seat belt has tension. The second type are tongue mechanisms progressively engage their cinch mechanism with each successive tensile force through the webbing. These tongues continually shorten the webbing (i.e., tighten the webbing around the occupant) over time, resulting from forces transmitted during normal vehicle driving (e.g., from hitting a bump or pot-hole, or from vehicle stability) through the webbing. Therefore the seat belt systems that employ these tongue mechanisms become more uncomfortable for the occupant during use or over time.
It would be advantageous to construct a tongue mechanism that has free-falling capability, and includes a cinch mechanism which engages at a pre-determined belt tension, then disengages when the belt tension drops below the pre-determined amount. It would also be advantageous for this tongue mechanism not to progressively tighten the webbing around the occupant over time during normal vehicle use.